Can somone me with this 1 problem? in the figure shown, △rst is an isosceles triangle with rs≅rt. which is the measure of ∠t? a.21° b.40° c.70° d.110°

In an isosceles triangle, the angles opposite to the two equal sides are also congruent.
Based on your information, T and S are congruent. So we know that the measure of angle T is 3x+7. But we need to solve for x. Let's add all the angle values together and set it to 180 because the angles of a triangle sum to 180.
1) 2(3x+7) + 2x - 2 = 180
2) 6x + 14 + 2x - 2 = 180
3) 8x + 12 = 180
4) 8x = 168
5) x = 21
6) m<T = 3x + 7 = 3(21) + 7 = 63 + 7 = 70
I got C, but it is always helpful to double check work. Hope this helps!